Method to prevent damage to probe card

ABSTRACT

Probe cards are configured with protective circuitry suitable for use in electrical testing of semiconductor dice without damage to the probe cards. Protective fuses are provided in electrical communication with conductive traces and probe elements (e.g., probe needles) of a probe card. The fuses may be active or passive fuses, and are preferably self-resetting, repairable, and/or replaceable. Typically, the fuses will be interposed in, or located adjacent to, conductive traces residing over a surface of the probe card. Methods of fabricating a probe card are provided, as well as various probe card configurations. A semiconductor die testing system using the probe card is also provided.

FIELD OF THE INVENTION:

The present invention relates generally to probe cards for testing theelectric characteristics of semiconductor dice. More specifically, thepresent invention relates to probe cards configured with protectivecircuitry suitable for use in electrical testing of semiconductor dicewithout damage to the probe cards.

BACKGROUND OF THE INVENTION

In the manufacture of semiconductor devices, a large number ofsemiconductor devices, also known as dice or integrated circuit chips(ICs or chips), are formed on a semiconductor wafer by using, forexample, precision photolithographic technologies. These fabricatedsemiconductor devices are subjected to a series of test procedures inorder to assess the electrical characteristics of the integratedcircuits contained on the semicondutor devices. Semiconductor deviceswhich have been found to be satisfactory by testing procedures areselectively transferred for subsequent processing such as die attach,wire bonding, and encapsulation. New integrated circuit designs andhigher unit volumes are additional considerations that drive testing ofICs. Also, as IC devices become more complex, the need for high-speedand accurate testing becomes increasingly important.

IC device testing procedures conventionally include “wafer-level probetesting” in which individual ICs or groups of ICs, while still on thewafer, are initially tested to determine functionality and/or speed.Wafer probing establishes a temporary electrical contact between the ICand the automatic test equipment and is a critical step for verifyingdesign and performance of the IC and for sorting ICs before singulationand costly packaging. Other tests, such as speed testing and “burn-in”testing are typically performed after the dice have been singulated fromthe wafer. IC testing further typically involves testing for variousperformance parameters while changing environmental conditions such astemperature, voltage and current.

Typically, testing at the wafer level involves the use of probe cardsand other test heads to electrically test ICs by making electricalconnection interfaces with groups of ICs or a single IC at a time. Ifthe wafer has a yield of ICs which indicates that the quality andquantity of functional ICs is likely to be good, the individual ICs aresingulated or “diced” from the wafer with a wafer saw. Each individualdie may be assembled in a package to form an IC device, or may be bumpedwith solder (usually prior to separation from the wafer) for directflip-chip bonding to a semiconductor substrate. Other various packagingmeans may also be used, as is known to those of skill in the art.

The test signals can include specific combinations of voltages and/orcurrents transmitted through the probe card to the ICs on the wafer.During the test procedure, response signals such as voltage, current andfrequency are analyzed and compared to required values by a testcontroller. Thus, by applying the appropriate voltages and/or currentsand monitoring the device response, a computer program running thetesting apparatus determines the functionality of the die. Theintegrated circuits that do not meet specification can be marked ormapped in software. Following testing, defective circuits in the ICs maybe repaired by actuating fuses (or anti-fuses) to inactivate thedefective circuitry and substitute redundant circuitry.

Conventional probe cards can be generally classified into twocategories: needle-type probe cards and membrane-type probe cards.Needle-type probe cards are the most common type of probe card, andinclude elongated probe needles mounted on an annular ring. A typicalprobe needle is a pointed needle-like element of small size, with a tipthat tapers down into a sharp point. When mounted on the annular ring,the probe needles typically have their free ends pointing downward andare carefully aligned with the ends of all the other probe needles to bein a single plane. An exemplary probe needle configuration is disclosedin U.S. Pat. No. 5,532,613 to Nagasawa et al., which includes a probeneedle having a pointed or conical tip. Probe needles are typically madeof tungsten, but materials such as beryllium copper, palladium, andrhenium tungsten are also used.

The probe needles are typically secured to the annular ring by epoxy orare bonded, as by welding, to a blade, and are adapted to make temporaryelectrical connections between contact locations on the dice (e.g., bondpads, fuse pads, test pads) and external test circuitry. The annularring, in turn, is attached to a printed circuit board (PCB) substrate.The PCB substrate typically includes electrical traces in electricalcommunication with the probe needles. An exemplary probe card havingprobe needles is described in U.S. Pat. No. 4,757,256 to Whann et al..

Membrane-type probe cards are typically formed as having tungstencontact bumps disposed on a thin, flexible dielectric material, such aspolyimide, as the membrane. Membrane-type probe cards commonly employ amultilayer, flexible PCB interconnection structure configured with finepitch traces leading to low inductance bump array structures alignedwith the location of the pads of the device under test (e.g., asemiconductor die being tested). In a conventional membrane probingsystem, contact bumps of the bump array structures are pressed down viaan elastic body interposed between the contact bumps and the membrane,such that any height variation among the contact bumps can be absorbedby the flexible thickness of the elastic body. Exemplary membrane-typeprobe cards are disclosed in U.S. Pat. No. 4,906,920 to Huff et al. andin U.S. Pat. No. 6,181,145 to Tomita et al..

Needle-type probe cards and membrane-type probe cards may be furtherconfigured to meet the needs of the particular devices under test. Inthis regard, the probe cards may be specially configured as verticalcontact probe cards (used, for example, to test LOGIC devices of a C4type), cantilever-type probe cards (generally used to test inner-leadsof LCD drivers with super fine-pitch (e.g., 40 micron-pitch) bumps),probe cards for wafer level burn-in, probe cards configured to testhigh-speed microprocessor units (MPUs) with high pin counts, as well asvarious other types of probe cards known in the art.

In all types of probe cards, the testing voltage current is carried froman external test circuit to the pad connecting sections (probe elements)of the probe cards through conductive traces or wiring in electricalcommunication therewith.

One concern in the art is over the application of excessive voltage tothe IC chip under test. In this regard, U.S. Pat. No. 6,127,837 toYamamoto et al. (“Yamamoto”) describes a series of resistance,transistor and capacitance structures formed on a probe wafer between atest bump and a shared power/signal line. According to Yamamoto, theresistance, transistor and capacitance structures prevent overshoot orundershoot of signals supplied to the bump, and also prevent theapplication of excessive voltage or current to the chip. Yamamoto,however, does not disclose methods or apparatus for protection of theprobe wafer, and further does not describe a probe card configured tocarry the current regulating structures.

The delivery of excessive voltage during probe testing to an IC may alsoresult in damage to the probe card. In Japanese Patent Application61174771, a small fuse is provided on the back side surface of a probecard in order to prevent the end of a probe needle connected to agrounding pad from seizing due to an over-current delivered to a shortcircuited IC. Japanese Patent Application 0115367 discloses a thermalfuse fixed between a probe needle and power source which generates heatand becomes fused before a probe pin generates heat and is fused. Eachof these patent applications, however, is drawn to means for preventingseizing and fusing of a probe needle routed to ground and power, and donot address the limitation of current through the probe card in generalor through any probe needle which might otherwise cause that probeneedle to become nonfunctional.

Japanese Patent Application 04265541 discloses an array of easilyexchanged fuses interposed between corresponding probes on a probe cardand a power supply. The apparatus disclosed therein, however, isrelatively bulky in that the fuses are vertically disposed over theprobe card and the apparatus includes a fuse body for holding the fuses.

Accordingly, what is needed in the art is a probe card configurationdesigned to limit current to a plurality of varying probe elements, notjust ground and power. It would also be advantageous to provide a probecard with one or more fuses that are self-resetting, or readilyreplaceable and/or repairable. Fuses which can be fabricatedsimultaneously with other components on the probe card using processeswhich are well known in the semiconductor arts are also desirable. Aprobe card thus manufactured would extend the life of the probe card,therefore, saving time, materials, and costs for those involved insemiconductor dice testing operations.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a method of forming aprobe card is provided. The method comprises providing a substratehaving a first surface and a second surface; disposing a plurality ofconductive traces adjacent at least one of the first surface and thesecond surface; providing a plurality of probe elements in electricalcommunication with the plurality of conductive traces; and providing aplurality of fuse elements in respective electrical communication withat least some of the plurality of conductive traces, at least some ofthe plurality of fuse elements disposed immediately adjacent at leastone of the first surface and the second surface. Additionally, the fuseselements may be passive or active fuses elements, and the fuse mayfurther be configured to be self-resetting, repairable and/orreplaceable. In a preferred embodiment, substantially all of theconductive traces are provided with a respective fuse element.

A method of fabricating a probe card is also provided. The methodcomprises providing a probe card substrate; providing a plurality ofconductive traces over a surface of the probe card substrate; providinga plurality of probe elements in electrical communication with theplurality of conductive traces wherein at least one of the probeelements is configured for supplying a test signal to at least onesemiconductor die and wherein a second probe element is configured forreceiving a test signal from the at least one semiconductor die; andproviding at least one repairable or replaceable component in electricalcommunication with at least some of the plurality of conductive traces.

In a still further embodiment, a method of using a probe card fortesting at least one semiconductor die is disclosed. The methodcomprises providing a probe card having a plurality of probe elementsconnected thereto, the probe elements configured for supplying testsignals to the at least one semiconductor die; providing a fuse inelectrical communication with at least some of the probe elements; andtesting the at least one semiconductor die by supplying test signals.

In accordance with another aspect of the invention, a probe card isprovided. The probe card includes a substrate having a first surface anda second surface; a plurality of conductive traces disposed adjacent atleast one of the first surface and the second surface; a plurality ofprobe elements in respective electrical communication with theconductive traces and a plurality of fuses in respective electricalcommunication with the conductive traces.

In yet another embodiment of the invention, a semiconductor die testingsystem is disclosed. The semiconductor die testing system comprises aprobe card including a substrate having a first surface and a secondsurface; a plurality of conductive traces disposed adjacent at least oneof the first surface and the second surface; a plurality of probeelements in electrical communication with the conductive traces; aplurality of fuses in electrical communication with the conductivetraces; and semiconductor device testing apparatus linkable with theprobe card, the semiconductor device testing apparatus configured forsending test signals through the probe card.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a schematic view of probe card according to an embodiment ofthe present invention;

FIGS. 2 and 3 are perspective views of fuse embodiments of the presentinvention;

FIGS. 4A and 4B are schematic views of fuse embodiments according to thepresent invention;

FIGS. 5A and 5B are simplified perspective views of active fuseembodiments of the present invention;

FIGS. 6A-6D are simplified diagrams of other active fuse embodiments ofthe present invention;

FIG. 7 is a simplified diagram of a test system in accordance with thepresent invention;

FIG. 8 illustrates a still further embodiment of the present invention;and

FIG. 9 shows a probe card embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

As noted throughout the disclosure, the present invention providesvarious advantages, including the ability to perform a multitude oftests, such as functional, parametric, burn-in, high frequency, andother tests, without risk of damage to the probe card. Performing ICtesting according to the present invention provides significant costsavings in protecting and allowing reuse of probe cards which mightotherwise be damaged by high test temperatures, electrical overloads,and various other sources of electrical failure or operator error duringthe testing process.

As used herein, use of the term “IC testing” encompasses both statictesting, where the IC is simply powered up, and dynamic testing, wherethe IC is powered up and is sent signals exercising some degree offunctionality over the IC.

Referring to drawing FIG. 1, an exemplary probe card 30 configured inaccordance with an embodiment of the present invention is shown in aschematic view. As described in more detail herein, probe card 30 actsas an interface to an IC testing computer which produces appropriatetest signals and senses the response of the ICs under test. The probecard 30 includes a substrate 32, typically a PCB substrate, preferablyformed of a rigid or semi-rigid material adapted to withstand thestresses associated with IC testing. Materials preferred for use infabricating substrate 32 include FR-4 and other glass-filled and ceramicresins, silicon (including monocrystalline silicon, silicon-on-glass,silicon-on-sapphire), germanium, gallium arsenide, or other materialsthat are well-known in the art. In one aspect of the embodiment,substrate 32 may be formed so as to have a coefficient of thermalexpansion matching, or closely matching, the ICs to be tested.

Substrate 32 is configured with a plurality of conductive traces 34formed on or adjacent to one or more surfaces thereof. As can be seen inFIG. 1, the conductive traces 34 extend inwardly from a plurality oftest contacts 36 towards a plurality of probe elements 38. Whensubstrate 32 is made of a semiconductor material, an electricallyinsulating layer, such as silicon dioxide, can be formed on substrate 32to provide an insulative surface for conductive traces 34 and testcontacts 36. The silicon dioxide layer can be formed by methodswell-known in the art of silicon-based manufacturing including, forexample, chemical vapor deposition (CVD) or exposing a silicon-basedsubstrate to an oxidizing atmosphere for a short time.

In accordance with recognized practices in the semiconductor art,conductive traces 34 may also be formed as a metallization layer underone or more surface layers of substrate 32. Thus, in a second aspect ofthe embodiment, probe card 30 may be constructed in multi-layeredfashion, with conductive traces 34 located in intermediate layers ofsubstrate 32. In the currently preferred configuration, the conductivetraces 34 are formed on a top surface 35 and/or bottom surface 37 of aprobe card 30. Typically, probe card 30 will include one conductivetrace 34 in electrical communication with each probe element 38,although more than one conductive trace 34 per probe element 38 iscontemplated within the scope of the present invention. In otherconfigurations (not shown), a single conductive trace 34 may provideelectrical signals for more than one probe element 38 during testing.

By use of the term “in electrical communication with,” it is meant thatthe subject electrical components are configured and positioned so as tocomplete an electrical circuit between one another when the componentsare supplied with power. Thus, components in electrical communicationwith one another will carry an electrical current originating from thesame source when the probe card 30 is operational.

As shown in FIG. 1, test contacts 36 are preferably disposed on aperiphery of substrate 32 for electrical interconnection with externaltesting equipment (not shown). The illustrated arrangement of testcontacts 36, however, is not intended to be limiting of the presentinvention, and test contacts 36 may alternatively be disposed on one orboth sides of substrate 32 and/or in a range of various locations,including locations in the area of a center-most portion of substrate32. Conductive traces 34, which are in electrical communication withtest contacts 36, thus provide electrical paths for test circuitry toprobe elements 38. Conductive traces 34 are preferably formed of ahighly conductive, low resistivity metal, such as aluminum, copper,titanium, tantalum, molybdenum, or alloys of any thereof. Conductivetraces 34 may be fabricated according to conventional methods well knownin the art, including, but not limited to, plating, thin film depositionprocesses (e.g., CVD, sputtering, photolithography processes andetching), and thick film processes (e.g., stenciling or screenprinting).

Various other types of conductive traces known in the art are alsocontemplated for use in the present invention. As a nonlimiting example,conductive traces 34 may include nonmetallic conductive traces which maybe formed of materials such as doped polysilicon. In this aspect of theembodiment, an LPCVD process may be used to form a conductive trace 34of phosphorous-doped polysilicon.

Still referring to FIG. 1, probe elements 38 are illustrated as aplurality of probe needles. The illustration, however, is not intendedto be limiting of the present invention, and one of skill in the artwill recognize the illustrated probe needles and probe card 30configuration maybe readily substituted for bumps, or other types ofelectrical contacts known in the art, which are configured for makingtemporary electrical connections with contact pads of ICs during ICtesting.

Probe elements 38 of probe card 30 are arranged in patternscorresponding to patterns of pads on ICs to be tested. For ease ofillustration and simplicity in describing the embodiment, only a singlepattern of probe elements 38 for testing a single IC is shown. Inpractice, however, probe card 30 will preferably be configured with aplurality of patterns of probe elements 38, with each pattern forming acorresponding plurality of test sites for testing a plurality ofrespective ICs. As such, probe elements 38 may be formed in varyingarrays and densities corresponding to the pads of the IC devices to betested. Each probe element 38 interfaces with a surface portion ofsubstrate 32 adjacent a conductive trace 34 at a probe element-substrateinterfacing portion 33 of probe card 30.

Probe elements 38 are shown mounted on a ring 40, preferably comprisingepoxy, and extending inwardly from a center cutout portion of substrate32. This illustrated arrangement, however, is not intended to belimiting of the present invention. Thus, probe elements 38 may beconfigured on probe card 30 in a multitude of conventional orunconventional configurations. Probe elements 38 may be formed of avariety of conductive materials, including, but not limited to, copperand tungsten. As is readily apparent to one of skill in the art, thediameter, taper, and material of the probe elements 38, when formed asprobe needles, may be varied to determine the spring rate of the probe.

With further reference to drawing FIG. 1, a fuse 42 is interposed in, orlocated adjacent to, each conductive trace 34. Preferably, fuses 42 areinterposed in, or located adjacent to, conductive traces 34 in regionsof probe card 30 which are directly adjacent to one of test contacts 36and probe elements 38. One of skill in the art will recognize numerousspecific locations for fuses 42, including placement immediatelyadjacent to, and in electrical communication with, terminating ends ofconductive traces 34 (e.g., at interfaces with test contacts 36 andprobe elements 38).

In a related aspect of the embodiment, fuses 42 are further preferablydisposed immediately adjacent at least one of a first and a secondsurface area of substrate 32 (e.g., a top surface 35 and a bottomsurface 37 of substrate 32). By use of the phrase “disposed immediatelyadjacent” at least one of a first surface and a second surface ofsubstrate 32, it is meant that a fuse 42 is located such that at least aportion of a fuse 42 is in contact with (either over or under) a surfaceof substrate 32, or that a fuse 42 is in close proximity to a surface ofsubstrate 32. A fuse 42 that is in “close proximity” to a surface ofsubstrate 32 may, for example, be surrounded by a fuse-holding body (notshown) that is in contact with a surface of substrate 32.

In a preferred embodiment, fuses 42 are interposed adjacently betweenconductive traces 34 and test contacts 36 and disposed immediatelyadjacent at least one of a first surface or a second surface ofsubstrate 32 in the case where the conductive traces 34 are carryingsignals and/or burn-in voltage into corresponding bond pads of asemiconductor device. In a related aspect of a preferred embodiment,fuses 42 carrying signals or burn-in voltage away from correspondingbond pads of a semiconductor device are disposed immediately adjacent atleast one of a first surface or a second surface of substrate 32 andbetween probe element-substrate interfacing portions 33 of probe card 30and conductive traces 34.

In a most preferred embodiment of the present invention, fuses 42 areconfigured to be self-resetting and/or easily repairable or replaceable,such that the probe card 30 may be readily reused for testing at a latertime after one or more fuse 42 have been tripped. Preferably, fuses 42are configured to trip (i.e., provide an “open” in the conductive tracecircuitry) at a current level below an absolute maximum current that theprobe card 30 or the IC device under test can handle without beingdamaged. The current-carrying capacity for a fuse 42 may vary dependingupon the particular test configuration involving probe card 30. Thecurrent-carrying capacity for fuse 42 typically will also vary inaccordance with various individual components (e.g., resistors,transistors, capacitors, probe elements 38, etc.) on probe card 30and/or the particular IC device under test.

Fuses 42 for use in the present invention may be generally classified asactive and/or passive fuses. As used herein, a “passive” fuse is arelatively thin conductor which may have its conductive propertiesdisabled upon the application of a predetermined threshold of energyinto it. In the context of the invention, the conductive properties ofpassive fuses may thus be disabled by passing a current of ahigher-than-desired threshold through the fuse, thus causing resistiveheating within the fuse that results in the fuse conductor melting,cracking, vaporizing, and/or becoming otherwise non-conductive.Preferably, passive fuses for use in the present invention includematerials such as titanium tungsten and platinum silicide. Othermaterials for passive fuses, such as aluminum, copper, nichrome, dopedpolysilicon, metal silicide or various other conductive metal or alloys,are well known in the art of semiconductor device manufacturing and arealso included in the scope of the present invention.

In one aspect of a preferred embodiment of the invention, the passivefuses are formed of the same conductive material(s) as the conductivetraces 34 and/or test contacts 36 described herein. Using depositionprocesses well known in the art, each of fuses 42 may be formed at thesame time (simultaneously) as the other fuses 42. In a related aspect ofthe embodiment, the passive fuses may thus be constructed at the sametime as the conductive traces 34 and/or the test contacts 36 using thesame deposition and/or other processing steps (e.g., CVD followed byphotopatterning). These passive fuses are typically formed and/orrepaired by patterning a deposited layer of the conductive material ofthe fuse over an insulating dielectric layer, typically silicon dioxide,of substrate 32.

In other embodiments of passive fuses, the passive fuses may beprefabricated and placed in electrical communication with testingcircuitry on at least one surface of a probe card 30 by mechanicalmeans.

It will be apparent to one of skill in the art that while preferred fuseembodiments are described below, the present invention is not intendedto be limited by the described embodiments. In this regard, the presentinvention incorporates by reference the various embodiments of fuses foruse with ICs as disclosed in U.S. Pat. No. 4,198,744 to Nicolay, U.S.Pat. No. 4,682,204 to Shiozaki et al. and U.S. Pat. No. 5,608,257 to Leeet al..

In its simplest form, a passive fuse for use in the present inventionmay comprise two ends of a conductive trace 34 joined by a “neck” havinga width considerably smaller than the width of the conductive trace 34.Referring now to drawing FIG. 2, a preferred configuration of a passivefuse 42 a of the present invention is illustrated with passive fuse 42 ainterposed in a conductive trace 34. A dielectric layer 45 is showndisposed under conductive trace 34 and passive fuse 42 a. Passive fuse42 a includes trace interfacing portions 44, 46 in an aspect of theembodiment where the passive fuse 42 a is formed of a material differingfrom that of conductive trace 34. Passive fuse 42 a further includes arelatively thin (in comparison to conductive trace 34 and/or traceinterfacing portions 44, 46) “neck” or wire portion 48 configured toconduct current up to a predetermined current threshold. Traceinterfacing portions 44, 46 are in electrical communication with traceend portions 50, 52 of conductive trace 34, the trace end portions 50,52 otherwise being “open” in relation to one another (i.e., not inelectrical communication with each other).

In an embodiment where the conductive trace 34 and the passive fuse 42 aare formed of the same materials, it should be understood that separatetrace interfacing portions 44, 46 of passive fuse 42 a need not beformed, and passive fuse 42 a may simply comprise a neck portion 48.

Preferably, the predetermined current threshold of passive fuse 42 acorresponds to a current level nominally below an absolute maximumcurrent that the probe card 30 or the IC device under test can handlewithout being damaged. Upon reaching the predetermined current level,passive fuse 42 a trips, disabling the circuit to which passive fuse 42a is electrically connected.

Passive fuses 42 a may be formed and/or repaired by conventional methodswell known in the art, such as conductive layer deposition techniques,photopatterning processes, and etching techniques. As previouslydiscussed, passive fuses 42 a may be formed concurrently with thedeposition of other conductive structures on probe card 30 (e.g.,conductive traces 34, test contacts 36, bond pads for probe elements,etc.), or passive fuses 42 a may be deposited or placed on probe card 30in a separate processing step. The neck portion 48 of a passive fuse 42a may be configured of varying widths dependent upon the nature of theapplication for which it will be used, and the materials used in itsconstruction. In a preferred aspect of the invention, a passive fuse 42a is configured with a neck portion 48 formed of a material selectedfrom the group consisting of titanium tungsten, aluminum, copper,nichrome, doped polysilicon, platinum silicide, and alloys orcombinations of any thereof. Further preferably, the neck portion 48 isconfigured of a width ranging from about 0.3 micron to about 10.0microns.

A second preferred passive fuse configuration is shown in drawing FIG.3. Here, a passive fuse 42 b is configured, in part, as a cutout of abond pad 54, wherein the bond pad 54 may be a test contact 36 or abonding interface for a conductive trace 34 and a probe element (notshown). In this embodiment, passive fuse 42 b forms a conductivefuse-type link between bond pad 54 and a conductive trace 34, and isthus also referred to herein as a “linking fuse” 42 b. As can be seen inFIG. 3, linking fuse 42 b is relatively narrower in width thanconductive trace 34 such that linking fuse 42 b will trip in the mannerpreviously described upon the application of an overcurrent into it.Linking fuse 42 b may be fabricated using a variety of techniques whichtypically involve deposition and photo-patterning as previouslydescribed. A dielectric layer 45 is disposed under conductive trace 34and passive fuse 42 b.

A third preferred embodiment of a passive fuse configuration for use inthe present invention is shown in section in drawing FIG. 4A. In thisembodiment, a passive fuse 42 c is shown as comprising a dual in-linepin header mounted in through-hole portions 56 of substrate 32. Passivefuse 42 c is configured with pin portions 60, 62 which are made ofconductive material. An insulated and removable connector shell 64containing a fuse conductor 66 may be positioned on pin portions 60, 62to carry current up to a predetermined threshold from pin portions 60,62. In the illustrated embodiment, through-hole portions 56 of substrate32 are positioned so as to provide an “open” in conductive trace 34.Through-hole portions 56 are configured with inner contacts 58 which arein electrical communication with conductive traces 34. When pin portions60, 62 of the dual in-line pin header passive fuse 42 c are placed inthrough-hole portions 56 of substrate 32, pin portions 60, 62 areconfigured to be in electrical communication with inner contacts 58,thus completing a current-carrying circuit through conductive trace 34.

As previously discussed, an overload of current sufficient to damage theprobe card 30, components thereof, or an IC device under test will tripthe fuse conductor 66, thus disabling the circuit extending throughpassive fuse 42 c. Upon blowing passive fuse 42 c, a new connector shell64 and/or new pin portions 60, 62 can be re-installed in through-holeportions 56 of substrate 32 to render probe card 30 operational again.

In a related embodiment, a passive fuse 42 d configured as adual-in-line socket is shown in drawing FIG. 4B. Passive fuse 42 dcomprises pin portions 68, 70 with an insulated connector shell 72 atone end thereof. Pin portions 68, 70 are formed of a conductive materialand are in electrical communication with a fuse conductor 74 residingwithin connector shell 72. Similar to the embodiment shown in FIG. 4A,through-hole portions 56 of substrate 32 are configured with innercontacts 58 and positioned so as to provide an electrical “open” inconductive trace 34. When passive fuse 42 d is pressed into through-holeportions 56, and the electrical circuit is completed wherein current cantravel from one end portion of a conductive trace 34, to a first innercontact 58, to a first pin portion 60, to fuse conductor 74, to a secondpin portion 60, to a second inner contact 58, and through to a secondend portion of a conductive trace 34. A current which is sufficientlyhigh to trip passive fuse 42 d will thus disable the circuit. To restorethe circuit, the blown passive fuse 42 d is removed, and a new passivefuse 42 d may simply be pressed into through-hole portions 56.

With regard to passive fuses 42 c and 42 d, one of skill in the art willreadily ascertain that the pin portions of these fuses are adaptable foruse with conductive traces 34 that are in intermediate layers insubstrate 32. In this regard, the pin portions of passive fuses 42 c and42 d may, for example, extend downwardly through through-hole portions56 in substrate 32 to contact conductive pads in electricalcommunication with a conductive trace 34 in an intermediate layer, thuscompleting a circuit through the trace.

Furthermore, passive fuses 42 c and 42 d are but two examples ofdiscrete electrical components that may be used as protective fuses forpurposes of the present invention. It will be readily apparent to oneskilled in the art that various other conventional designs for discreteelectrical components may be readily utilized herein. By use of the term“discrete electrical component,” it is meant that the particularelectrical component is manufactured separately from the probe card 30and thus subsequently attached thereto or otherwise integrated therein.

With reference to FIGS. 2, 3, 4A and 4B, each of passive fuses 42 a, 42b, 42 c and 42 d is configured to conduct current under a thresholdwhich will cause damage to probe card 30, and to become disabled when atest current exceeds a threshold under the probe card's maximumcurrent-carrying capacity. Typically, a higher than desired current in aconductive trace 34 (and/or in other components in which a passive fuse42 a, 42 b, 42 c or 42 d is placed) will cause the passive fuse 42 a, 42b, 42 c or 42 d to trip by resistive heating within the fuse, theresistive heating resulting in the fuse conductor (i.e., neck portion48) melting, cracking, vaporizing or the like. As previously discussed,passive fuses 42 a, 42 b, 42 c and 42 d may be replaced or repaired suchthat probe card 30 may be reused at a later time.

“Active” fuses may also be used to protect probe cards and thecomponents thereon in accordance with the principles of the presentinvention. “Active fuses,” as used herein, are electronic circuitsconfigured to conduct current up to a predetermined level wherein oncethe predetermined level of current has been exceeded, active fuses areconfigured to stop conducting current, thus disabling the circuit towhich the active fuse are connected. Unlike passive fuses, however,active fuses are configured to automatically reset upon removal of thecurrent overload. Upon self-resetting, the active fuses are againoperational to carry current to and from the probe elements on the probecard. Typically, the active fuses for use in the present invention arefast tripping surface mount-type fuses.

In one aspect of the embodiment, a bimetallic switch may be used as anactive fuse according to the present invention. The bimetallic switch asan active fuse may be interposed in, or located adjacent to, aconductive trace 34 in order to limit undesirably high current levelspotentially traveling through a probe card 30. A simplified bimetallicswitch 76 is shown in FIGS. 5A and 5B in electrical communication withportions of a conductive trace 34 over a dielectric surface 45 of aprobe card 30. As is well known in the art, bimetallic switch 76 isformed of a first metal conductor 78 and a second metal conductor 80having differing rates of thermal expansion.

As shown in FIG. 5A, first metal conductor 78 and a second metalconductor 80 are configured to be in contact with one another forconducting current up to a predetermined current threshold. When thecurrent becomes excessive (e.g., potentially damaging to the probe card30 and/or an IC device under test), the temperature of first metalconductor 78 and second metal conductor 80 rises, causing first metalconductor 78 (having a relatively higher rate of thermal expansion) tobend away from second metal conductor 80. As first metal conductor 78and second metal conductor 80 bend away from each other, the contactbetween first metal conductor 78 and second metal conductor 80eventually opens, thus interrupting current flow in conductive trace 34(FIG. 5B). Eventually, the disruption of electrical current toconductive trace 34 resulting from the “open contact” causes thetemperature of first metal conductor 78 and second metal conductor 80 tofall, thus allowing the contacts to reclose and permitting the currentto flow again.

A series of embodiments of an active fuse on a probe card are shown indrawing FIGS. 6A, 6B, 6C and 6D. Therein, the active fuse comprises aPolymer Positive Temperature Coefficient (PPTC) fuse as an overcurrentprotection mechanism interposed in, or located adjacent to, a conductivetrace 34 on a probe card 30. Like components of each of FIGS. 6A, 6B, 6Cand 6D are referenced by the same reference characters.

Various lead arrangements for PPTC fuses are shown in FIGS. 6A, 6C and6D. In FIG. 6A, a PPTC active fuse 82 a is shown having a radial leadarrangement positioned in a through-hole portion 56 of substrate 32 andin electrical communication with inner contacts 58. In FIG. 6B, the PPTCactive fuse 82 a of FIG. 6A is shown in tripped condition. A PPTC activefuse 82 b having an axial lead arrangement with terminals 84, 86 inelectrical communication with conductive trace 34 is shown in FIG. 6C. APPTC active fuse 82 c in a surface mount configuration known in the artis shown in FIG. 6D. Fuses 82 b and 82 c may be electrically connectedto conductive traces 34 in a manner well known in the art, to includethe use of conventional soldering techniques.

Generally, the PPTC active fuses 82 a, 82 b and 82 c for use in thepresent invention are constructed with highly conductive carbonparticles 88 combined with a nonconductive polymer 90 that exhibits twophases. In a first phase, which occurs under a predetermined currentthreshold, the polymer 90 exhibits a crystalline or semi-crystallinestructure in which the molecules form long chains and are arranged in aregular structure (FIG. 6A). In this phase, the carbon particles 88 arepacked within the crystalline polymer structure, thus forming aconductive chain spanning between opposing electrodes of the PPTC fuse82 a.

When electricity is conducted through the crystalline structure, whichhas a low resistance configuration, the temperature increases within thePPTC fuse. At a predetermined temperature which is correlated with acurrent overload, this structure transitions by expanding to anamorphous phase which breaks the chain of carbon particles 88. Theresulting random alignment of carbon particles 88 caused by the phasechange instantly opens the circuit (FIG. 6B).

After the circuit has been opened for a certain period of time, thepolymer 90 cools and returns to its normal crystalline state, thusallowing the carbon particles 88 to again touch and form conductivepaths, upon which the circuit closes and the probe card can functionproperly. Thus, the PPTC fuses are advantageously self-resetting, and donot have to be replaced as is the case with conventional passive fuses.

Preferably, the PPTC fuses for use in the present invention will havetrip times of just a few milliseconds. Such PPTC fuses are presentlyavailable from several commercial sources, including Raychem Corporation(Menlo Park, Calif.) and Bourns Incorporated (Ogden, Utah.).

It should be understood that while the above-described embodimentsillustrate only a single fuse interposed in, or located adjacent to, aconductive trace on a probe card, the present invention contemplates aplurality of fuses interposed in, or located adjacent to, a plurality ofrespective conductive traces. The fuses may be passive fuses, activefuses, or combinations thereof. The use of an active fuse may beparticularly desirable in the situation where a particular location ofthe fuse on the probe card renders the fuse not easily repairable orreplaceable. Passive fuses may be particularly desirable in thesituation where extremely short trip times are desirable and/or thelocation of the fuse renders it readily repairable or replaceable. Forexample, passive fuses may be preferable for placement in probe cardconductive traces used for supplying relatively high voltages during ICtesting (e.g., voltages supplied for burn-in testing of ICs).

In the preferred embodiments, at least one fuse according to the presentinvention is interposed in, or located adjacent to, each conductivetrace. In some contemplated configurations, however, some, but not all,of the conductive traces may include a fuse configured according to thepresent invention. For example, a fuse may not be needed in one or moreconductive traces on a probe card where the one or more conductivetraces will be transporting extremely low voltage signals to an ICdevice under test.

Referring to drawing FIG. 7, a simplified diagram of a test system 100in accordance with the present invention is shown. The test system 100typically includes a wafer handler (not shown) for handling andpositioning a semiconductor wafer 112, test equipment 114 for generatingtest signals, and a probe card 116 for making temporary electricalconnections with the semiconductor wafer 112. Semiconductor wafer 112 isconfigured with a plurality of bond pads 113 on an active surfacerepresenting a plurality of unsingulated ICs 118. Probe card 116 isconfigured with a plurality of conductive traces 120 over at least onesurface thereof. Interposed in, and/or located adjacent to, at leastsome, and preferably all, of the conductive traces 120 are fuses 122provided in accordance with the above-described principles of thepresent invention.

A prober 124 (shown as transparent for purposes of clarity) typicallylowers the probe card 116 on the semiconductor wafer 112 until probeelements 126 of probe card 116 come in contact with bond pads 113 onsemiconductor wafer 112. Probe elements 126 are shown as needles, butmay alternatively be configured as bumps, or other types of electricalcontacts known in the art for making temporary electrical connectionswith bond pads 113 of semiconductor wafer 112. Test equipment 114 is inelectrical communication with the test contacts 117 on probe card 116and, upon activation, transmits test signals through the test contacts117 and conductive traces 120 to probe elements 126. Alternately, thesemiconductor wafer 112 may be raised into contact with the probeelements 126 of probe card 116 of a prober 124.

Preferably, but not necessarily, the semiconductor wafer 112 or theprobe card 116 is stepped so that unsingulated dice on the semiconductorwafer 112 are tested in groups of two or more at a time in sequence. Thetest system 100 may also be configured to test all unsingulated dice onsemiconductor wafer 112 at the same time. Upon probe elements 126 comingin contact with bond pads 113 of semiconductor wafer 112, testcontroller 114 applies test signals and/or a power source voltagethrough probe card 116 to bond pads 113, and analyzes the resultingsignals therefrom. During the testing process, fuses 122 protect probecard 116 and/or the ICs 118 on semiconductor wafer 112 from overcurrentsand/or short circuits in the ICs 118.

Thus, upon an overload of current sufficient to damage the probe card116, components thereof, or an IC device on semiconductor wafer 112, oneor more fuses 122 exposed to the current overload will trip, thusdisabling the circuit extending through probe card 116. If the one ormore of the tripped fuses are configured as “active” fuses, the fuseswill automatically reset after the fuse cools, thus rendering probe card116 operational again. If the one or more tripped fuses are configuredas “passive” fuses, the probe card 116 may be reused after the trippedfuses are repaired or replaced (depending upon the particular type ofpassive fuse used).

The described test system 100, however, is only exemplary, and the testapparatus may be configured for any of a variety of device tests onsemiconductor wafer 112. Such testing may, for example, include, basicparametric tests, low frequency functional testing, speed binning testsusing specially designed test structures, boundary scan testing, anddevice testing at full operating frequency.

It will be appreciated by those skilled in the art that the embodimentsherein described, while illustrating certain embodiments, are notintended to so limit the invention or the scope of the appended claims.As such, the various embodiments are merely exemplary of the presentinvention, and thus, the specific features described herein are merelyused to more easily describe such embodiments and to provide an overallunderstanding of the present invention.

Those skilled in the art will also understand that various combinationsor modifications of the preferred embodiments could be made withoutdeparting from the scope of the invention. For example, those skilled inthe art will appreciate that a plurality of the fuses described hereinmay interposed side by side in a conductive trace of a probe card.

In yet another embodiment which is illustrative of the scope of thepresent invention, a plurality of protective fuses 138 (provided inaccordance with the principles of the present invention) can beconfigured as, interposed in, or placed adjacent to, pogo pin 140portions of a probe card assembly 135 (drawing FIG. 8). As shown indrawing FIG. 8, pogo pins 140 form an interface between testingcircuitry (not shown) and test contacts 142 on a probe card 136. Onceapprized of the present invention, methods of providing protective fuses138 as interposed in, or placed adjacent to, a pogo pin 140 will beapparent to one skilled in the art. For example, pogo pins 140 may beformed, in part, as a fuse body for holding one or more protective fuses138.

In drawing FIG. 8, protective fuses 138 are illustrated as forming aportion of pogo pins 140. Pogo pins 140 enable a probe card 136 to beelectrically connected with test equipment (not shown). Thus, pogo pins140, including protective fuses 138, are electrically connected toconductive traces 144 on probe card 136 via test contacts 142 residingon a probe card surface. Test signals are transmitted from the testequipment to probe card 136 by way of pogo pins 140 and protective fuses138. Protective fuses 138 are configured prevent excessive currents frombeing transmitted to probe card 136, thus preventing damage to probecard 136. Protective fuses 138 further prevent excessive currents fromtraveling through probe needles 146 to one or more IC devices 148 undertest. In a preferred aspect of the embodiment, protective fuses 138which have been tripped due to excessive current may be replaced by, forexample, inserting a new protective fuse 138 into a pogo pin 140 in theaspect of the embodiment where a pogo pin 140 is configured in part as afuse body.

Furthermore, the probe cards for use in the present invention maycomprise any type of probe card susceptible to the introduction of oneor more fuses for the electrical protection the probe card and/orcomponents thereof. Thus, the methods and apparatus described herein arecontemplated in a wide ranging variety of probe card configurations,including, but not limited to, vertical contact probe cards,cantilever-type probe cards, and probe cards for wafer level burn-in.

Additionally, the fuses described herein are suitable for use with avariety of other electrical components which may be found on a probecard. These components include resistors, transistors, capacitors,diodes, and the like.

As a final example, this invention, while being primarily described withreference to a probe card configured probe needles, has equalapplicability to various other types of probe card configurations,including membrane-type probe cards. In this regard, a simplifiedschematic view of an exemplary membrane-type probe card 150 is shown indrawing FIG. 9. Membrane-type probe card 150 includes a carriersubstrate 151 supporting a membrane 154 and a plurality of contact bumps152 connected through the membrane 154 to conductive traces 156.Conductive traces 156 are in electrical communication with test contacts158. Conductive traces 156 thus carry test signals from multichanneltesting equipment (not shown) to contact bumps 152. In turn, contactbumps 152 supply test signals from the testing equipment to contact pads162 on an IC device under test 164. Interposed in, or adjacent to,conductive traces 156 are fuses 160 configured in accordance with theprinciples of the present invention.

Thus, while certain representative embodiments and details have beenshown for purposes of illustrating the invention, it will be apparent tothose skilled in the art that various changes in the invention disclosedherein may be made without departing from the scope of the invention,which is defined in the appended claims.

1. A method of forming a probe card for use in the testing of asemiconductor device comprising: providing a substrate having a firstsurface, a second surface, and an aperture therethrough; disposing aplurality of conductive traces adjacent at least one of the firstsurface and the second surface; providing a plurality of probe elementsin electrical communication with the plurality of conductive traces, atleast a first one of the plurality of probe elements configured forsupplying a test signal, and at least a second one of the plurity ofprobe elements configured for receiving a test signal, the plurality ofprobe elements having a portion thereof located on the first surface ofthe substrate, having a portion thereof extending through the aperturein the substrate, and having a portion thereof located on the secondsurface of the substrate; and providing a plurality of fuse elements inrespective electrical communication with at least some of the pluralityof conductive traces, at least some of the plurality of fuse elementsdisposed immediately adjacent at least one of the first surface and thesecond surface, the at least some of the plurality of fuse elementscomprising at least two types of fuses of an active fuse element, apassive fuse element, a self-resetting fuse element, a repairable fuseelement, and a replaceable fuse element, each fuse element of theplurality of fuse elements for limiting the current level thereof to oneof an absolute maximum current level for the probe card withoutsubstantial damage thereto and an absolute current level for use in thetesting of a semiconductor device without substantial damage thereto. 2.The method of claim 1, wherein the providing a plurality of fuseelements comprises providing a fuse element of the plurality of fuseelements in respective electrical communication with substantially eachof the plurality of conductive traces.
 3. The method of claim 1, whereinthe providing a plurality of fuse elements comprises providing at leastone fuse element of the plurality of fuse elements configured to bereplaceable or repairable after being tripped.
 4. The method of claim 3,wherein the at least one fuse element of the plurality of fuse elementsis formed of a material selected from the group consisting of titaniumtungsten, aluminum, platinum suicide, copper, nichrome, dopedpolysilicon, metal silicide, and alloys of any thereof.
 5. The method ofclaim 3, wherein the providing a plurality of fuse elements comprisesforming at least some of the plurality of fuse elements using adeposition process.
 6. The method of claim 3, further comprisingconstructing at least some of the plurality of conductive traces and atleast some of the plurality of fuse elements at substantially the sametime and by a single deposition process.
 7. The method of claim 3,further comprising providing a plurality of test contacts adjacent theat least one of the first surface and the second surface of thesubstrate, at least some of the plurality of test contacts in electricalcommunication with respective conductive traces of the plurality ofconductive traces, and further comprising forming each of the pluralityof conductive traces, the plurality of fuse elements, and the pluralityof test contacts of the same materials.
 8. The method of claim 1,wherein the providing a plurality of fuse elements comprises insertingat least one of the plurality of fuse elements in through-hole portionsconfigured in the at least one of the first surface and the secondsurface of the substrate.
 9. The method of claim 1, wherein theproviding a plurality of fuse elements comprises providing at least oneof the plurality of fuse elements configured as a dual in -line pinheader fuse.
 10. The method of claim 1, wherein the providing aplurality of fuse elements comprises providing at least one of theplurality of fuse elements configured as a dual in-line socket fuse. 11.The method of claim 1, wherein at least one fuse element of theplurality of fuse elements is configured to be self-resetting afterbeing tripped.
 12. The method of claim 11, wherein the at least one fuseelement is configured as a PPTC fuse.
 13. The method of claim 11,wherein the at least one fuse element is configured as a bimetallicswitch.